Recently, the demand for portable electronic products such as notebooks, video cameras, cellular phones or the like has rapidly increased, and electric vehicles, energy storage batteries, robots, satellites have been actively developed. For this reason, high-performance secondary batteries allowing repeated charging and discharging are being actively studied.
Currently, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium secondary batteries, and the like are used as commercial secondary batteries. Among them, lithium secondary batteries have little to no memory effect in comparison with nickel-based secondary batteries, and thus lithium secondary batteries are gaining a lot of attention for their advantages of free charging or discharging, low self-discharging, and high energy density.
A lithium secondary battery generally uses lithium oxide and carbonaceous material as a positive electrode active material and negative electrode active material, respectively. The lithium secondary battery includes an electrode assembly in which a positive electrode plate and a negative electrode plate respectively coated with the positive electrode active material and the negative electrode active material are disposed with a separator being interposed between them, and an exterior, namely a battery case, which seals and accommodates the electrode assembly together with an electrolyte.
Generally, a lithium secondary battery may be classified into a can-type secondary battery where the electrode assembly is included in a metal can and a pouch-type battery where the electrode assembly is included in a pouch of an aluminum laminate sheet, depending on the shape of the exterior.
Recently, secondary batteries are widely used not only for small-sized devices such as cellular phones but also middle-sized or large-sized devices such as vehicles and power storages. In particular, along with the exhaustion of carbon energy and the increased interest on environments, hybrid electric vehicles and electric vehicles attract attention globally, for example in US, Europe, Japan and Korea. In such a hybrid electric vehicle or electric vehicle, a battery pack for giving a driving force to a vehicle motor is the most essential part. Since a hybrid electric vehicle or electric vehicle may obtain a driving force by means of charging and discharging of the battery pack, the hybrid electric vehicle or electric vehicle ensures excellent fuel efficiency and exhausts no or reduced pollutants, and for this reason, hybrid electric vehicles and electric vehicles are used more and more. In addition, the battery pack of the hybrid electric vehicle or electric vehicle includes a plurality of secondary batteries, and the plurality of secondary batteries are connected to each other in series or in parallel to improve capacity and output.
Generally, a battery pack includes a cell assembly configured by stacking a plurality of secondary batteries, a sensing assembly for sensing voltages of the secondary batteries of the cell assembly, and a pack housing configured to accommodate the cell assembly and the sensing assembly in an inner space thereof. In addition, in order to assemble the battery pack as described above, the cell assembly to which the sensing assembly is coupled may be accommodated in the inner space of the pack housing. Here, the pack housing may be formed with material and structure having so sufficient rigidity to protect components such as the cell assembly and the sensing assembly, accommodated in the inner space, against external physical factors, as a case of the battery pack.
Meanwhile, the cell assembly may be coupled to the pack housing by combining its lower portion with the lower portion of the inner space of the pack housing. For this, the cell assembly should be placed at a specific location in the inner space of the pack housing. However, in an existing battery pack, it is not easy to accurately position the cell assembly in the pack housing for assembling between the cell assembly and the pack housing. In particular, since a space between an inner side surface of the pack housing and an outer side surface of the cell assembly is very small, once the cell assembly is accommodated in the inner space of the pack housing, it is not easy to move the cell assembly to an accurate location. Moreover, if the cell assembly is erroneously located in the inner space of the pack housing and is thus moved to a correct location, the cell assembly or the pack housing may be damaged.